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March 21, 1939. KARG Re. 21,034

MEANS FOR AUTOMATIC EXPOSURE CONTROL I Original Filed June 5, 1955 2 Sheets-Sheet. l

I Josef [far i mi F 1 7 "m 22 f I ATTORNEYS.

March 21, 1939. J; KARG MEANS FOR A UTO MATIC EXPOSURE CONTROL Original Filed June 5, 1935 '2 Sheets-Sheet Josef Karg INVENmR. WW

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A TTORNEYS.

Reiuued Mar. 21, 1939 PATENT OFFlCE r LIEANS FOR AUTOMATIC EXPOSURE CONTROL Josef Karg, Vienna, Germany, assignor, by direct and mesne assignments, to Eastman Kodak Company, Rochester, N. Y., a corporation oi New Jersey No. 2,061,909, dated November 24, 1936. Serial No. 25,080, June 5, 1935. Application for reissue December 8, 1938, Serial No. 244,698. In

Austria June 9, 1934' Claims. (CI. 95-64)- .The present invention relates to a novel means for controlling the degree of exposure in photographic apparatus and more particularly to a system and method of automatic or semi-automatic exposure control utilizing a light responsive electric element serving for controlling or actuating an exposure control mechanism.

One object of the invention is to'provide an automatic exposure control mechanism for photographic cameras controlled by a photoelectric element adapted to supply the requisite controlling energy for adjusting an element capable of controlling the degree of exposure.

Another object of the invention is the, provision of automatic or semi-automatic exposure control means for photographic apparatus in which the controlling action is eflfected by means of an electric light sensitive element without requiring an outside source of electrical stimulation, such as a battery.

Another object of the invention is theprovision or an exposure control mechanism for photo v graphic cameras whereby the .operator may choose a desired diaphragm opening or stop value to suit special requirements, such as depth of focus and whereby a corresponding shutter speed is adjusted automatically dependent on existing light conditions.

Another object of the invention is the provision of an automatic exposurecontrol mechanism for photographic cameras whereby the photographer is enabled to choose a desired shutter speed to suit special conditions, such as the speed of movement 01' the object to be photographed and whereby the diaphragmopening or stop isautomatically adjusted dependent on the existing light values of the subject or scene being photographed.

A further object of the invention is the provision of means in a photographic camera equipped with automatic or semi-automatic exposure control, whereby the operator -is apprised of the impossibility of securing a correctly exposed picture'under the existing light or other exposure determining conditions, such as speed of movement, of the object to be photographed, etc.

A further object of the invention is the provision of means in a photographic camera, es-

pecially of the type equipped with automatic ex- 'posure control, whereby operation 01' the camera and the carrying out 01' an exposure is automatie cally prevented under existing unfavorable conditions of light, or other exposure determining conditions.

- Another object of the invention is to provide an automatic exposure control mechanism for element or other light evaluating device serves to preset an exposure control element such as an iris diaphragm while the final adlustment is carried out by the operator when making the exposure by operating an exposure release element.

A further object of the invention is the provision of indicating means in connection with an automatic exposure control mechanism for photographic cameras wherein a light responsive element serves to preset anautomatically adjusted exposure controlling element in accordance with prevailing light conditions and the setting of a manually adjustable correlated exposure control element in such a manner that by subsequent operation of the camera shutter, said first exposure control element is automatically adjusted to ,secure a correct exposure, whereby .said indicating means serve to apprise the operator of the value or adjustment of the automatically adjusted exposure control means prior to a the initiation oi the exposure so as to enable the photographer to set the manually operated exposure control element to suit special requirements as depth of focus, speed of the object to be photographed, etc.

The above and further objects of the invention and novel aspectsthereof will become more ap-' parent from the following detailed description taken with reference to the accompanying drawings wherein I have illustrated several emv improvements of the invention, connected with an iris diaphragm device.

Fig. 2 is a wiring diagram showing the connection of the photoelectric cell and electromagnetic control device serving for presetting the iris control as illustrated in Fig. l.

Figs. 3 and 4 illustrate the mechanism according to Fig.1 in an intermediate and final position, respectively, when making an exposure by operating the shutter or exposure release of thecamera.

Figures 5 and 6 show modified constructions of a device of .the type illustrated by Figure 1;

Figures 7 to 9 illustrate further improvements of an exposure control mechanism of p the type shown in Figure 1 wherein the automatic adjustment of the diaphragm opening is variably modi- .have shown therein in a diagrammatical manner an embodiment of an automatic diaphragm or stop control mechanism in its simplest form in accordance with the invention. The electromagnetic actuating device shown comprises a moving coll l disposed in a known manner between the poles of a permanent magnet 2 and pivoted about an axis 3. 'I'hemovlng coil, which may be of the type provided in the known D'Arsonval galvanometer, is energized directly froma photo-electric element 4, preferably of the type adapted to generate the requisite electrical energy for operating the moving coil without the aid of an additional electrical stimulation, such as a battery. Photoelectric devices of this type, known as photovoltaic cells, especially those of the barrier plane type, are primarily suited for the purpose of my invention, and consist substantially of a metal base coated with a thin layer of light sensitive semi-conducting material, such as crystalline selenium, cup rous oxide and the like, and a translucent conductive covering layer firmly applied to the light sensitive layer. It light rays are impinged upon the light sensitive material passing through the translucent cover, a potential difference is generated between the base plate and the covering layer wherebythe moving coil is deflected at varying angles, dependent on the voltage or current generated by the photo-electric element which is in turn proportional to the amount of incident light impinged upon the light sensitive surface. The photo-electric element as described is mounted on the camera body in a suitable manner so as to be exposed to the same light rays reflected from the subject or scene to be photographed in the picture taking position of the camera.

In order to take account of the exposure speed and the sensitivity of the negative material, such as the film or plate used, an electrical resistance 5 may be connected in the circuit of the photoelectric element as shown in Figure 2.

According to my invention I provide an element having low mass controlled by the light sensitive system to serve as a stop or abutment for the diaphragm control. This abutment element may, for instance,-be directly connected to the moving coil of the electromagnetic device. In addition, I provide means, such as a clamping arrangement, for holding the exposure control or abutment element in a flxed position duringthe exposure period beginning with the operation of the shutter release and the initiation of the exposure. This exposure controlling element may consist of a leaf or vane pivotally mounted about an axis through its center of gravity by means of frictionless bearings, such as by a direct connection to the shaft of the moving coil device. This controlling vane should consist of light material and lervesls a variable stop or abutment for limiting the movement of the iris diaphragm or other exposure controlling element as will be described hereafter. Anarrangementofthistypeofexposure control insures the advantage of bothready response to slight impulses before the beginning of the exposure and great mechanical resistance during the shutter operation.

In the drawings Figures 1, 3 and 4 which are sections taken between the front lens and diaphragm setting ring of a shutter connected with the lens mount in a known manner, I have shown an abutment vane in the form of stepped disk I III suitably balanced, such as by means of the counterweight 6 and carried by the moving coil I. The diaphragm setting ring I II carries a finger I I2 which in the normal position; i. e. when the diathe photo-electric element in its dark or unexcited condition, the highest step of the vane III! has a position opposite the finger H2 and that with increasing excitation the next following steps, and with the maximum excitation of the photo-electric element, the lowest step of the vane 0 will be opposite the finger II2. In

the drawings I have only shown four steps for the sake of simplicity, and it is understood that the number of steps may be increased to secure any desired degree of accuracy. The winding of the shutter by pushing upward the winding lever Ill does not interfere with the free movement of the vane. The position shown in Figure l corresponds to the wound condition of the shutter spring 3'. A locking lever I I5 serves to prevent a premature operation by action of a spring H6. The shutter release lever H3 is shown in its normal or resting position in which it is held by the action of spring III. The release lever is provided with an extension finger I I8 engaging a nose II! of the diaphragm setting ring III, thus preventing the latter from prematurely leaving 4 its initial or normal position. The release lever H3 furthermore carries a pin mounted thereon and arranged to move in a guide I2I in such a manner as to unlock the lever II5 after moving a predetermined distance. Figure 3 5 shows the mechanism in a position shortly prior to, and Figure 4 shows the position immediately following the release of the shutter. The spring I22 serves to provide an elastic connection between the shutter release lever and the. diaphragm 5 setting ring. This spring is tensionedby the operation of the shutter release lever, wherebythe finger H8 is disengaged from the nose I I9 in such a manner as to enable the diaphragm setting ring I20 pivotally to leave its normal position by the action of spring 6 I22, and to close the diaphragm as shown at I24 in Figure 3 until the finger II2 of the diaphragm setting ring engages one of the steps of the vane Illl dependent on the existing excitation of the photo-electric element. In this manner the vane 6 I I8, and with it themoving coil,will remain locked until the shutter release lever has returned to its normal position. The height of the separate steps is designed in such a manner that the aperture of the iris diaphragm adjusted in each case is related 7 to the fllumination of the photo-electric cell according to a linear law. In order to keep the dimensions of the stepped disk within practical limits. it is advisable to reduce the maximum angular movement of the finger- Il2 relative to the 1 maximum rotational movement of the iris diaphras nr such as by a suitable coupling with a corresponding transmission ratio connecting the diaphragm I24 with the setting ring III. The length of the release pin I20 is designed in such a manner that with the engagement of the finger I i2 with the lowest step 01' the vane IIO, the adjustment of the diaphragm has been completed before the lever H5 is unlocked by the pin I20. The elastic connection between the shutter release lever and the diaphragm setting ring has the I eil'ect that the release lever may be moved until unlocking the lever 5 even after the finger II2 has engaged a step of the vane 0. In addition, the spring I22 serves for relieving the axis of the moving coil from lateral pressure exerted during the operation of the release lever. Whenever the lever III is released after operation 01 the shutter, it will return to its initial position through the action of the spring I". Simultaneously the spring I22 is compressed, whereby the finger II8 of the release lever re-engages the nose II! of the diaphragm setting ring, thus returning the iris diaphragm to its normal position at full aperture. In order to prevent the diaphragm from opening due to a premature release of the release-lever during the exposure period, a suitable locking element, not shown in the drawings, may be provided for blocking the movement of the release lever during the return movement of the winding lever Ill from its operating position to its normal position.

Referring to Figure 5, I have shown a modified arrangement wherein the connection by the spring I22 is omitted. In this case the diaphragm setting ring III is connected with a lever I26 through a spring I25 being untensioned when the shutter is in its unwound condition. The lever I26 is connected with the shutter winding lever I through a linkage element shown at I21".

described in connection with Figures 1, 3 and 4.

The advantage of this construction is the fact that with the spring I25 in its untensioned condition, a closingoi the diaphragm is prevented, thus preventing unnecessary operations oi the diaphragm mechanism and wear on the moving coil device by accidental operation oi the release lever when the shutter is in its unwound condition.

It the prevailing light conditions are insumcient for, making a proper exposure, the release of the shutter is automatically blocked by a mechanism of modified construction as shown in Figure 6. In the latter the guide I2I for the release pin I20 is mounted on a rod I21 arranged to slide within a pair 01- guides I20 and I20. A spring I30 tends to press the rod I21 against the diaphragm adjusting finger H2 in such a manner that the rod will follow the movement of the finger under the influence of the spring I20 until stopped by a projection iii of the guide I29. The construction of the vane H is such that its first and its last step are so dimensioned as to prevent a displacement of the rod I21. Thus, if at the moment of operating the release lever, the moving coil has assumed such a position that one oi the end steps of the vane H0 is oppositethe finger II2, the guide I2I will lever H5, and causes a shutter release.

setting adjusted by the photographer.

remain in the position as shown in the drawings; The release pin will therefore move past the locking lever Iii, thus preventing a release of. the shutter. At the same time a bell signal is produced in that an extension of the release pin I20 engages a clapper I" with its nose I02 actuating a bell I. Inevery other position of the vane IIO, the release'pin I20 due to the changed position'oi the guide I2i engages the locking At the same time the path of the nose I32 is changed so as to prevent engagement with the clapper and accordingly the operation of the alarm. The first'abutment step 01' the vane I-III engaging the finger I I! in the non-excited or dark condition of the photo-electric element is. preferably designed with a sufliciently large angle as shown at a in the drawings so as to engage the finger i I2 already at low excitation values of the photoelectric element in which case a lens of greater relative opening or speed would be required to secure a fully exposed picture. In this case the second step of the/vane IIO would correspond to full lens opening and the closing of the diaphragm started beginning with the third step.

In Figure 7 I have shown a mechanism for automatically modifying the operation of the abutment vane in accordance with manual adjustments of a correlated exposure control element, in the example described, the shutter speed In this and the following figures the camera shutter has not been shown for the sake of simplicity and clarity oi illustration. It is understood that both with regard to the present and previous exemplifications illustrated, the invention may be practiced in connection with any type of central or focal plane shutter.

Referring to Figure 7, I have shown an actuatingarm I35 carried by the diaphragm setting ring III. The diaphragm adjusting finger H2 in this constructional embodiment is connected to an intermediate member arranged for both rotational and axial movement. The stepped vane in this embodiment consists of as many separate elements connected to each other and difl'ering from each other as to the height and/or number of the steps as there are values for the manually adjusted control element viz.; shutter speed values in the example described. In the drawings, I have only shown two vane elements I31 and I38 mounted upon the moving coil shaft I, but it will be understood that any number oi such elements may be provided to secure any desired number of shutter speed adjustments. By

. operating the lever I39 i'or adiusting the correlated exposure control element such as the shutter-speed, the intermediate member I30 is displaced parallel to the lens axis in such a manner that the finger H2 is brought opposite a vane element corresponding to the respective adjustment of the correlated exposure control element, viz., the setting of the shutter in the shown, may be providedior returning the mem-' ber I36 to its initial position after disengagement with the actuating rod I35.

A further embodiment of a device of this type steps should vary according to a. logarithmic law rangement for indicating the position 01' the abutso as to obtain practical results by mechanical addition. This makes it necessary to transmit the movement of the diaphragm setting ring upon the actuating rod by a properly constructed connecting mechanism, such as a lever I42, en-

;gaging a suitably curved slot I4I associated with the diaphragm setting ring, as shown.

It is iurthermore possible as is understood to utilize the adjustment of the lever I39 for adapting the shutter mechanism to other exposure controlling factors such as plates or films oi diflerent sensitivity.

According to a further constructional feature illustrated in Figure 9, the moving coil shaft 3 is provided with a simple abutment member cooperating with a stepped member manually adjustable in accordance with the selected shutter speed. The construction shown has the further advantage of reducing mechanical stress upon the axis of the moving coil device. The abutment member consists of a flat element I 44 connected to the moving coil shaft through a leaf spring I43 and arranged for free movement opposite two fixed abutment elements I45 and I46 in the normal position. If the diaphragm setting ring III is rotated by operation 01' the shutter release lever in a manner similar as heretofore described, the stepped member I48 pivotally mounted about a shaft I48 is swung through the action of a guide slot I41 engaged by an opposite lever arm of the member I48, whereby the latter engages the element I44 with one of its steps dependent on the position of the element I44. Due to the resiliency of the leaf. spring I43, the member I48 will press the element I44 firmly against the abutments I45 and I45, thus arresting and blocking the movement of the iris diaphragm. The steps of the member I48 not engaging the member I44 may pass. freely between the abutments I45 and I46.

When the diaphragm setting ring returns to its normal position, the element I44 disengages the members I45 and I46 through the action of the spring I43 so that the former is allowed to move freely again.

Referring to Figure 10, I have shown an arment vane so as to inform the operator of the adjustment in advance of the operation of the shutter. Simultaneously the position of the correlated or manual exposure control means may be indicated by a suitable scale. When adjusting the independent or manual control means, such as in the example illustrated by rotation of the shutter speed setting ring I49, to a desired shutter speed, a scale I52 is simultaneously displaced bymeans of guide tracks I5I and a slot guide shown at I50. The scale I52 is provided with graduations indicating the automatically adjustable exposure control values, in the example chosen; the

stop or diaphragm aperture numbers. I have or the like. -This indicator is eccentrically arranged and its marginal curve is designed in such a manner that its intersection with the scale I52 indicates the stop or aperture value which the diaphragm: would automatically assume upon subsequent operation oi the shutter at this instant.

As is understood, the mechanism for automatic exposure control of the above described characterlstics may be used with any type of exposure adjusting device allowing a gradual or step-bystep control of correlated exposure control values. Moreover, it will be understood that either of a pair of exposure control elements may be embodied in the inventive device for automatic or manual adjustment and that the invention is not limited to the specific example 01 automatic iris control and manual shutter speed setting, it being obvious and within the scope or the invention to adiust the iris diaphragm manually and to connect a gradually adjustable shutter speed control element such as the shutter speed setting ring in shutters of well known type with the mechanism according to the invention.

As will be evident from the above description, the invention is not limited to the specific. embodiments presented herein for illustration, but

the underlying principle and inventive concept is susceptible oi numerous modifications diflering from the specific disclosure herein presented and coming within the broad scope and spirit of the invention as defined in the appended claims.

I claim:

1. In a photographic camera, a lens; an adjustable exposure control element for controlling the quantity of light passed through said lens; a shutter; shutter actuating means; an electrically actuated means; a stepped movable member controlled by said electrically actuated meansand adapted to control the limit positionto which said exposure control element may be adjusted; a light sensitive device adapted to vary the current in said electrically actuated means in accordance with the intensity oi light passed through said lens; and means actuatable by said shutter actuating means for automatically adjusting said exposure control element to the limit position determined by said stepped member.

2. In a photographic camera, a lens; an exposure control element gradually adjustable between zero and a limit position for controlling the quantity of light passed through said lens; a shutter; shutter actuating means'; an electrically actuated means; a stepped movable member controlled by said electrically actuated means and adapted to control the limit positions of said exposure control device in steps; a light sensitive means adapted to vary the current in said electrically actuated means in accordance with the intensity of-the light passed through said lens; means actuatable by said shutter actuating means for automatically adjusting said exposure control element to the limit position determined by said stepped member prior to the initiation of the exposure; and means for returning said exposureable according to the intensity 0! the light passed through said lens; a stepped movable element controlled by said last means and adapted for controlling the adjusting limit of said exposure control element in successive steps; means actu-.

ment to the'limit position determined by said stepped element prior to the initiation of an exposure; and means for restoring said exposure control element to its initial position upon completion of each exposure.

'4. In a photographic camera, a lens; an adjustable iris diaphragm normally in open position for controlling the quantity 01' light passed through said lens; a shutter; shutter actuating means; an electrically actuated means; a stepped movable element controlled by said electrically actuated means and adapted to adjust variable limit positions of said diaphragm in successive steps; a light sensitive device adapted to vary the current in said electrically actuated means in accordance with the intensity of light passed through said lens; means actuatable by said shutter actuating means for automatically adlusting said diaphragm to the limit position determined by said stepped element prior to the initiation of an exposure; and means for returning said iris diaphragm to its normal position upon completion of each exposure.

5. In a photographic camera as claimed in claim 1 including means controlled by a predetermined step of said stepped member for blocking said shutter actuating means at a predetermined intensity oi! light passed through said lens.

8. In a photographic camera as claimed in claim 1 comprising signaling means controlled by a predetermined step of said stepped member corresponding to a predetermined intensity of the light passed through said lens.

7. In a photographic camera as claimed in claim 1 comprising signaling means controlled by the first and last step of said stepped member having a predetermined dimension dependent on insufiicient and excessive intensity, respectively, of the light passed through said lens. K L

8. In a photographic camera as claimed in claim 1 comprising blocking means controlled by the first and last step 01' said stepped member having a predetermined dimension for preventing the actuation oi the shutter dependent on insufiicient and excessive intensity, respectively, of light passed through said lens.

9. In a photographic camera as claimed in claim 1 including a scale calibrated in adjusting values of said exposure control means and a movable index member having a marginal curve of predetermined configuration controlled by said electrically actuated-means and in accordance with the light passed through saidlens said-index member intersecting said scale to indicate the adjustment or said exposure control means in advance of the actuation of said shutter.

10. In a photographic camera having a lens; a shutter; shutter actuating means for controlling theqimntityotlightpassedthroughssidlens;

means for controlling the quantity of light passed through said lens, said means comprising a shutter speed adjusting means and an iris diaphragm; diaphragm aperture adjusting means; an electrically actuated device comprising a magnet and a moving coil operatively associated therewith; a stepped rotatable member controlled by said moving coil; light sensitive means adapted to vary the current in said moving coil to adjust said stepped member in accordance with the intensity 01 light passed through said lens; means for actuating said diaphragm controlling means by said shutter actuating means prior to the initiation of an exposure; abutment means connected to said diaphragm controlling means and adapted to engage a step of said stepped member to limit the adjustment of said diaphragm by said shutter actuating means dependent on the position of said stepped member; and means for returning said diaphragm to its normal position by the return movement of said shutter actuating means upon completion 01' each exposure.

11. In a photographic camera as claimed in claim 10 including a plurality of stepped members each coordinated to a difi'erent shutter speed; means actuatable by said speed adjusting means to place one 0! said stepped members in operative position with said diaphragm controlling means prior to the initiation of an exposure.

12. In a photographic camera as claimed in claim 10 including a scale ca'dbrated inv diaphragm aperture values, said scale being ar-.

ranged to be displaced in predetermined relation to said shutter speed adjusting means; and a movable index member of predetermined configuration controlled by said moving coil and variably intersecting said scale for indicating the adjustment of said iris diaphragm in advance of the actuation of said shutter.

i 13. In a photographic camera as claimed in claim 1 including means engaging said stepped member prior to its engagement with said abutment means for holding said stepped member in rigid position during its engagement with said diaphragm controlling means.

14. In a photographic camera having a lens; automatic means for adjusting the quantity of light passed through said lens in accordance with the light values of the object to be photographed; and means controlled by said automatic means to indicate unfavorable light conditions to prevent wrongly exposed pictures.

15. In a photographic camera having a lens; automatic means for adjusting the quantity of light passed through said lens in accordance with the light values of the object to be photographed; and blocking means controlled by said automatic means to prevent over exposed pictures.

JOSEF KARG. 

